1. Field of the Invention
The present invention relates to remotely releasable pipe connectors, and more particularly, but not by way of limitation, to a remotely releasable pipe connector for use in setting conductor casing into the sea floor as used in the drilling of offshore wells.
2. Setting of the Invention
In the drilling of offshore oil and gas wells, a length of conductor casing is often driven into the sea floor from a barge or platform located on the surface. This conductor casing is usually of a large diameter; i.e., about 20 in. to over 30 in. Once installed, a continuous string of pipe, often referred to as a riser, is set within the conductor casing and extends to the surface. Drilling, completion and other well operations are carried out by drill pipe, tools, etc., passed through and contained within the riser.
In more detail, when the conductor casing is driven in a batch casing driving operation, such as through a subsea template, the conductor casing driven into the sea floor must be disconnected from the string of pipe above it at a certain point above the sea floor. Heretofore, this disconnection procedure has been carried out by either divers cutting the casing, which often requires from about four to six hours of actual underwater time for the divers and the expense associated therewith, or the use of hydraulically or wireline releasable conductor connectors, again which requires divers. Frequently, when divers are used, the connector fails to correctly disconnect because of improper operation of the release mechanism or by current induced bending moments.
Also, if the conductor casing is cut, there is no commercially available reconnection device to allow for simple reentry of the well. When this occurs, the casing must be cut which requires additional time and expense.
Several remotely operable pipe connectors which are operated mechanically or hydraulically from the surface to cause the release of the connector have been utilized heretofore. However such connectors are expensive and require either a cable or a hydraulic fluid hose which extends from the pipe connector to the surface. The presence of a cable or hose introduces casing string handling problems and protracts casing running time resulting in a significant extra expense.
While tubular pin and box pipe connectors including complementary locking dogs and slots which can be engaged or disengaged by relative movement between the pin and box have been known and used heretofore, such connectors are subject to being unintentionally disconnected during the manipulation of a string of pipe in which they are contained and their use has thus been limited.
There is a need for a remotely operable releasable pipe connector which does not require the use of divers or cables or hydraulic hoses. Further, there is a need for such a pipe connector which can withstand the forces needed to drive a surface casing into the sea floor.